Cardiac ablation catheters for forming overlapping lesions

ABSTRACT

Methods and instruments are disclosed for creating lesions in tissue, especially cardiac tissue, for treatment of arrhythmias and the like, by employing an elastic balloon and an energy emitter, which is independently positionable within the lumen of the instrument and adapted to project a series of spots of ablative energy through a transmissive region of the balloon to a target tissue site. The energy emitter preferably is configured such the spots of energy result in a series of lesions formed in the target tissue region when the emitter is activated, the lesions having an average area ranging from about 5 mm 2  to about 100 mm 2 . In one aspect of the invention, percutaneous ablation instruments are disclosed in the form of catheter bodies having one or more balloon structures at the distal end region of the instrument and an energy emitting element, which is independently positionable and rotatable within a lumen of the instrument and adapted to project ablative energy through a transmissive region of the balloon to a target tissue site in contact with, or proximal to, the balloon surface.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/357,156, filed on Feb. 3, 2003 and currently pending, whichis a continuation-in-part of U.S. patent application Ser. No.09/924,394, filed on Aug. 7, 2001, now U.S. Pat. No. 6,579,285 issuedJun. 17, 2003. Additionally, U.S. patent application Ser. No. 10/357,156is a continuation-in-part of U.S. patent application Ser. No.09/616,275, filed on Jul. 14, 2000, now U.S. Pat. No. 6,626,900 issuedSep. 30, 2003, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/602,420 filed on Jun. 23, 2000, now U.S. Pat.No. 6,572,609 issued Jun. 3, 2003, which is a continuation-in-part ofU.S. patent application Ser. No. 09/357,355, filed on Jul. 14, 1999, nowU.S. Pat. No. 6,423,055 issued Jul. 23, 2002. The teachings of all ofthese prior related applications are hereby expressly incorporated byreference.

BACKGROUND OF THE INVENTION

The present disclosure relates to ablation instruments and methods ofuse thereof, in particular to ablation catheters and methods for thetreatment of atrial fibrillation.

Cardiac arrhythmias, e.g., fibrillation, are irregularities in thenormal beating pattern of the heart and can manifest themselves ineither the atria or the ventricles of the heart. For example, atrialfibrillation is a form of arrhythmia characterized by rapid randomizedcontractions of atrial myocardium, causing an irregular, often rapidventricular rate. The regular pumping function of the atria is replacedby a disorganized, ineffective quivering as a result of chaoticconduction of electrical signals through the upper chambers of theheart. Atrial fibrillation is often associated with other forms ofcardiovascular disease, including congestive heart failure, rheumaticheart disease, coronary artery disease, left ventricular hypertrophy,cardiomyopathy, or hypertension.

Effective catheter treatment of atrial fibrillation was made possible bya breakthrough discovery in the late 1990's by investigators inBordeaux, France. They found that recurrent atrial fibrillation(paroxysmal and persistent) is triggered by rapidly firing tissue,(called “ectopic foci”), that are located in one or more of the fourpulmonary veins, which attach to the rear of the left atrium. Theirresearch, since confirmed by others, suggested that 85% or more of theectopic foci that initiate atrial fibrillation are located in or at theostium, (mouth), of the pulmonary veins. They demonstrated that atrialfibrillation could be cured by electrically isolating the pulmonaryveins from the rest of the atrium.

Various techniques have been proposed for pulmonary vein isolation.Although these procedures were originally performed with a scalpel,various other techniques have also been developed to form lesions.Collectively, these treatments are referred to as “ablation.” Innon-surgical ablations, the tissue is treated, generally with heat orcold, to cause coagulation and/or tissue necrosis (i.e., celldestruction). In each of these techniques, cardiac muscle cells arereplaced with scar tissue which cannot conduct normal electricalactivity within the heart.

In one known approach, circumferential ablation of tissue within thepulmonary veins or at the ostia of such veins has been practiced totreat atrial fibrillation. By ablating the heart tissue at selectedlocations, electrical conductivity from one segment to another can beblocked and the resulting segments become too small to sustain thefibrillatory process on their own.

Several types of ablation devices have recently been proposed forcreating lesions to treat cardiac arrhythmias, including devices whichemploy electrical current (e.g., radio-frequency (“RF”)) heating orcryogenic cooling. Such ablation devices have been proposed to createelongated lesions that extend through a sufficient thickness of themyocardium to block electrical conduction. Many of the recently proposedablation instruments are percutaneous devices that are designed tocreate such lesions from within the heart. Such devices are positionedin the heart by catheterization of the patient, e.g., by passing theablation instrument into the heart via a blood vessel, such as thefemoral vein.

Devices that rely upon resistive or conductive heat transfer can beprone to serious post-operative complications. In order to quicklyperform an ablation with such “contact” devices, a significant amount ofenergy must be applied directly to the target tissue site. In order toachieve transmural penetration, the surface that is contacted willexperience a greater degree of heating (or freezing). For example, in RFheating of the heart wall, a transmural lesion requires that the tissuetemperature be raised to about 50° C. throughout the thickness of thewall. To achieve this, the temperature at the contact surface willtypically be raised to greater than 100° C. In this temperature regime,there is a substantial risk of tissue destruction (e.g., due to watervaporization micro-explosions or due to carbonization). Charring of thesurface of the heart tissue, in particular, can lead to the creation ofblood clots on the surface and post-operative complications, includingstroke. Even if structural damage is avoided, the extent of the lesion(i.e., the width of the ablated zone) on the surface that has beencontacted will typically be greater than necessary.

Cardiac ablation instruments also suffer from a variety of designlimitations. For example, the shape of the heart muscle adds to thedifficulty in accessing cardiac structures, such as the pulmonary veinson the anterior surface of the heart. Typically, percutaneous devicesare positioned with the assistance of a guide wire, which is firstadvanced into heart. In one common approach, described, for example, inU.S. Pat. No. 6,012,457 issued to Lesh on Jan. 11, 2000 and inInternational Application Pub. No. WO 00/67656 assigned to Atrionix,Inc., a guide wire or similar guide device is advanced through the leftatrium of the heart and into a pulmonary vein. A catheter instrumentwith an expandable element is then advanced over the guide wire and intothe pulmonary vein where the expandable element (e.g., a balloon) isinflated. The balloon includes a circumferential ablation element, e.g.,an RF electrode, carried on the outer surface of the balloon, whichperforms the ablation procedure. The balloon must be large enough andsufficiently rigid to hold the electrode in contact with the innersurface of the pulmonary vein for the length of the procedure. Moreover,because the lesion is formed by an ablation element carried on thesurface of the balloon element, the balloon shape inherently limits thelocations where a lesion can be formed, i.e., the lesion must be formedat least partially within the pulmonary vein.

In another approach described in U.S. Pat. No. 6,235,025 issued toSwartz et al. on May 22, 2001, a guide wire is again used topercutaneously access a pulmonary vein and a catheter is again slid overthe guide wire to a position within the pulmonary vein. The catheterdevice includes two spaced-apart balloons, which are inflated in thevein (or in the vein and at its mouth). The space between the twoballoons can then be filled with a conductive fluid to delivery RFenergy (or, alternatively, ultrasound) to the vein and thereby induce aconduction block in the blood vessel by tissue ablation. With the Swartzet al. device, like the Lesh device, the region where tissue ablationcan occur is limited by the design. Because two balloons must seal aspace that is then filled with an ablative fluid, the lesion isnecessarily formed within the pulmonary vein.

Ablation within the pulmonary vein can result in complications.Overtreatment deep within a vein can result in stenosis (closure of thevein itself), necrosis or other structural damage, any of which cannecessitate immediate open chest surgery.

A limitation of these commonly utilized instruments is the lack of siteselectability. Practically speaking, each such percutaneous instrumentis inherently limited by its design to forming an ablative lesion at oneand only one location. For example, when an expandable balloon carryingan RF heating device on its surface is deployed at the mouth of a vein,the lesion can only be formed at a location defined by the geometry ofthe device. It is not possible to form the lesion at another locationbecause the heating element must contact the target tissue. Similarly,the above-described tandem balloon device can only form a lesion at alocation defined by the space between the balloons that is filled withthe ablative fluid.

Another limitation of such known instruments and methods is theirinability to accommodate the varied geometry of the heart. For example,the inner surface of the atrium is not regular. In particular, themouths of the pulmonary veins do not exhibit regularity; they often bearlittle resemblance to conical or funnel-shaped openings. Thus, when theabove-described expandable, contact heating devices encounter anirregularly-shaped ostia, the result can be an incompletely formed(non-circumferential) lesion.

Moreover, the size or shape of the pulmonary vein ostia that areencountered may be too big or too small for the selected ballooncatheter and it may be necessary to remove the first balloon catheterfrom the patient and replace it with another instrument having a balloonelement of a different size. Replacement of the catheter with anotherbefore a procedure can begin (or in the middle of a multiple veinablation protocol) can substantially increase the overall duration ofthe procedure and/or increase the chance of trauma.

Accordingly, there exists a need for better cardiac ablation instrumentsthat can quickly and effective create pulmonary vein encircling lesionseven in the face of irregularly shaped or variable sized target tissueregions.

SUMMARY OF THE INVENTION

Methods and instruments are disclosed for creating lesions in tissue,especially cardiac tissue, for treatment of arrhythmias and the like, byemploying an elastic balloon and an energy emitter, which isindependently positionable within the lumen of the instrument andadapted to project a series of spots of ablative energy through atransmissive region of the balloon to a target tissue site. The energyemitter preferably is configured such that the spots of energy result ina series of lesions formed in the target tissue region when the emitteris activated, the lesions having an average area ranging from about 5mm² to about 100 mm² and, in some instances, 10 mm² to about 80 mm². Incertain embodiments, the energy emitter is also be configured to formarc shaped lesions in the target tissue region, each arc shaped lesionsubtending an angle ranging from about 5 degrees to about 45 degrees,preferably less than 30 degrees relative to the rotatable emitter (e.g.,based on the emitter or longitudinal axis of optical element serving asthe center of a circular frame of reference).

In one aspect of the invention, percutaneous ablation instruments aredisclosed in the form of catheter bodies having one or more balloonstructures at the distal end region of the instrument. The balloonstructure and catheter bodies are at least partially transmissive toablative energy. The instruments can further include an energy emittingelement, which is independently positionable and rotatable within thelumen of the instrument and adapted to project ablative energy through atransmissive region of the balloon to a target tissue site in contactwith the balloon surface. The energy is delivered without the need forcontact between the energy emitter and the target tissue because themethods and devices of the present invention do not rely upon conductiveor resistive heating. Because the position of the radiant energy emittercan be varied, the clinician can select the location of the desiredlesion.

The present invention provides a mechanism for addressing the problem ofinstrument orientation and/or irregularly-shaped pulmonary veins byrotation and, in some instances, adjustment of the location of theenergy emitter to form a series of spot lesions that overlap and createa circumferential block. For example, the devices of the presentinvention can form a first series of lesions along a first arc when theenergy emitter is in a first location and a second series of lesionsalong a second arc when the energy emitter is in a second location. Thespot lesions can be combined to form a continuous encircling orcircumscribing lesion that blocks fibrillation-inducing electricconduction.

In another aspect of the invention, spot lesions are formed by applyingradiant energy to target tissue in a range from about 50 Joules/cm² toabout 1000 Joules/cm², or preferably from about 75 Joules/cm² to about750 Joules/cm² In certain embodiments, the power levels applied by theenergy emitter can range from about 10 Watts/cm² to about 150 Watts/cm²and the duration of energy delivery can range from about 1 second toabout 1 minute, preferably from about 5 seconds to about 45 seconds, ormore preferably from about 10 to about 30 seconds. For example, forpower levels between 10 and 75 Watts/cm² it can be advantageous to applythe radiant energy for about 30 seconds. Lesser durations, e.g., of10-20 seconds can be used for power levels of 75 to 150 Watts/cm².

In another aspect of the invention the balloon structure is a compliantballoon that is designed and configured to at least partially conform tothe shape of the target tissue region upon expansion. For example, theballoon structure can be an elastic balloon (or balloon portion)configured to expand to cover pulmonary vein ostia of various sizesand/or shapes when filled with an inflation fluid. The balloon structurecan also be blunt-nosed or include a tapered distal portion to helpstabilize the balloon in the vein while still achieving contact with theostial region of the vein.

In a further aspect of the invention, the percutaneous catheters of thepresent invention can also include a reflection sensor, such as anendoscope positionable in the instrument's distal end region to obtainan image. The image allows the clinician to visualize the anatomy of thevein, the location of side branches and the position of the instrumentrelative to the vein. The clinician can determine whether contact hasbeen achieved (or blood has been cleared from an ablative energytransmission path) and the optimum location for ablation or radiationdosing before ablation begins or while ablation is occurring.

In one embodiment, percutaneous ablation catheters are disclosed havingat least one central lumen and one or more compliant balloon structuresat the distal end region of the instrument. Also disposed in the distalend region is an illuminating light source and an endoscope capable ofcollecting sufficient light to relay an image to the user. Theinstruments can further include one or more energy emitting elements,which are preferably independently positionable within the lumen of theinstrument (e.g., along a longitudinal axis of the balloon) and adaptedto project ablative energy through a transmissive region of theinstrument body (and/or balloon) to a target tissue site. The energy canbe delivered without the need for contact between the energy emitter andthe target tissue so long as a clear transmission pathway (e.g., throughthe fluid of the inflated balloon) is established. The endoscope elementof the instrument allows the clinician to see if such a pathway isclear.

Moreover, when the position of the radiant energy emitter can be varied,endoscopic guidance permits the clinician to select a desired locationand dose for the lesion. Endoscopic inspection thus permits theclinician to define a priori an “ablation plan” before creating anoverlapping series of spot lesions. Based on the locations and sizes ofthe lesions, the present inventions permits the user to select asuitable energy level, e.g., to compensate for the power changes due tothe size of the lesion and/or to compensate for the amount ofattenuation caused by projecting energy to a target site across agreater distance.

In another aspect of the invention, generally applicable to a wide rangeof cardiac ablation instruments, mechanisms are disclosed fordetermining whether the instrument has been properly seated within theheart, e.g., whether the device is in contact with a pulmonary veinand/or the atrial surface, in order to form a lesion by radiant energy.The projected energy can be electromagnetic radiation (e.g., visiblelight, infrared, ultraviolet or microwave) or ultrasound. The energy canbe focused by either refractive or reflective elements. Thiscontact-sensing feature can be implemented by an illumination source andan endoscope situated within the instrument. The image captured by theendoscope from the reflected light can be used to determine whethercontact has been achieved and whether such contact is continuous over adesired ablation path. The image data can further be used to confirmlesion formation and/or determine the extent of the spot lesions. Theimage data can also be enhanced by selective wavelength capture, opticalfiltering, or other image data processing techniques.

Monitoring allows the clinician to observe balloon inflation andestablish an optimal size (with sufficient contact for ablation).Reflective monitoring and/or imaging, especially with wide field of viewoptics, can be used to determine if the instrument is too deep within apulmonary vein by mapping tissue contact on the balloon. For example,tissue contact with proximal (rear) portions of the balloon can indicateover-insertion of the balloon in to a vein. Because the device has awide angle field of view and a large depth of field the clinician canalso see the relationship of the balloon to the pulmonary vein ostia.This capability allows the clinician to determine if the balloon is toodeep in the pulmonary vein because the optical sensor has the ability tosee a large portion of the interior the balloon. For example, if a largeextent of tissue contact is observed (or otherwise sensed) proximal tothe equator of the balloon (the circumferential zone of greatestdiameter), this can indicate that the instrument is too deep in the veinand the creation of lesions in this configuration may pose a risk ofcausing pulmonary vein stenosis.

In addition, because inflation of the compliant balloon can be observedunder direct visualization, the clinician can determine if the balloonis stretching the vein radially by assessing if full contact is achievedbefore the balloon is completely inflated. This stretching conditionwould also indicate that the balloon is too distal in the pulmonary veinand could cause damage.

When used in conjunction with a radiant energy emitter, the endoscopeand ablation element can be introduced as an assembly. In suchconfigurations, the energy emitter can also serve as the illuminationsource by operating at a low power level to provide the light for imageacquisition. In some embodiments, either the endoscope or the ablativeelement (or both) can be independently positionable within theinstrument.

In addition to determining the degree of contact between the instrumentand the tissue, the endoscope can be used to determine the extent oftissue ablation by sensing the change in color of the tissue as it isablated. Moreover, the endoscope can be used to detect the formation ofpotentially dangerous coagulated blood at the site of ablation and toallow the clinician to terminate the ablation if necessary for safetyreasons. The endoscopic image can also be used to extract colorimetricdata, e.g., to distinguish between tissue and blood.

In a further embodiment of the invention, the compliant balloon isexpandable to fill the space between the energy emitter and the targettissue with an energy-transmissive fluid and, thereby, provide atransmission pathway for projected radiant energy. The balloon canfurther be used to collapse trabecular tissue. The instrument canfurther include a radiant energy delivery element movable within thelumen of the catheter body such that it can be disposed at the desiredlocation and deliver radiant energy through a transmissive region of theinstrument to a target tissue site. The movable energy emitter thuspermits multi-step treatments, e.g., encircling an asymmetric veinstructure with a series of arc-shaped lesions, without the need forrepositioning of the balloon or any other portion of the instrument. Theinstrument can further include additional elements, such fluid deliveryports, to provide a blood-free transmission pathway from the energyemitter to the tissue target. In accordance with the invention, anendoscope is disposed within the projection balloon to monitor and/orguide instrument placement.

In other embodiments, a non-elastic or partially non-elastic balloon canbe useful in compressing or collapsing tissue to define a focal regioninto which a uniform dose of ablative energy can be projected orreflected. More generally, such balloon structures can be used to smoothirregular tissue surfaces and/or define focal planes or curved focalsurfaces for the delivery of ablative energy to cardiac tissue incontact with such surfaces.

The use of radiant energy, in conjunction with balloon catheterstructures of the present invention that are substantially transparentto such radiation at the therapeutic wavelengths, is particularlyadvantageous in affording greater freedom in selecting the location ofthe lesion, e.g., the site is no longer limited to the pulmonary veinitself. Because the energy can be projected onto the tissue in a seriesof overlapping spots, a ring-like lesion can be formed in atrial tissueat a distance from the vein, thereby reducing the potential for stenosisand/or other damage to the vein itself. Endoscopic-guidance allows theclinician to select a desired lesion location and implement a desiredablation plan by appropriate placement of the radiant energy emitter.

In certain embodiments, infrared radiation is particularly useful informing photoablative lesions. In certain preferred embodiments, theinstruments emit radiation at a wavelength in a range from about 800 nmto about 1100 nm, and preferably emit at a wavelength in a range ofabout 960 nm to about 1000 nm or in a range of about 1030 nm to about1090 nm. Radiation at a wavelength of 960 nm, 980 nm or 1000 nm iscommonly preferred, in some applications, because of the optimalabsorption of infrared radiation by cardiac tissue at these wavelengths.Such infrared radiation can also be useful as illumination light for theendoscope when provided at a sufficiently low power to capture imageswithout untoward damage to the image capture elements of the invention.Alternatively, ablation can be performed with infrared radiation whileone or more white light sources can serve as the illumination component.

In another embodiment, focused ultrasound energy can be used to ablatecardiac tissue. In certain preferred embodiments, an ultrasoundtransducer can be employed to transmit frequencies within the range ofabout 5 to about 20 MHz, and preferably in some applications within therange of about 7 MHz to about 10 MHz. In addition, the ultrasonicemitter can include focusing and/or reflective elements to shape theemitted energy into an annular beam or other desired shape.

However, in certain applications, other forms of radiant energy can alsobe useful including, but not limited to, other wavelengths of light,other frequencies of ultrasound, x-rays, gamma-rays, microwave radiationand hypersound.

In the case of radiant light, the energy delivering element can includea light transmitting optical fiber adapted to receive ablative radiationfrom a radiation source and a light emitting tip at a distal end of thefiber for emitting radiation. The light delivering element can beslidably and rotatably disposed within an inner lumen of the catheterbody and the instrument can further include translatory and rotationalmechanisms for disposing the tip of the light delivering element at oneor more of a plurality of locations with the catheter.

The present invention provides mechanisms for visualizing where theenergy will be applied prior to treatment. In one embodiment, the energydelivering element can include an aiming light source to project visiblelight onto the tissue, and reflected light can be observed via theendoscope. This visible light from the aiming beam provides anindication to the clinician of the exact location of energy delivery.Markers on the balloon are also disclosed for such visualization basedon known correlations between the variable position of the energy sourceand particular regions of the balloon. In another embodiment, virtualmarkers are employed. Based on such visual data, the location ofablation element can be selected to optimize the lesion formed uponactivation of the ablation element.

In certain preferred embodiments the balloon is filled with aradiation-transmissive fluid so that radiant energy from the energyemitter can be efficiently passed through the instrument to the targetregion. The fluid can also be used to cool the energy emitter throughconduction or via a closed or open circulator system. In certainapplications, it can be desirable to use deuterium oxide (so-called“heavy water”) as a balloon-filling fluid medium because of its lossabsorption characteristics vis-à-vis infrared radiation. In otherapplications, the inflation fluid can be water or saline or an admixtureof such fluids with deuterium oxide (to enhance ablative energytransmission) and/or sodium diatrazoate (to enhance radiographicimaging). The inflation fluid can also be circulated, e.g., via a pumpin a base station, to maintain the balloon in an inflated state whilealso extracting heat. In certain preferred embodiments the balloon isformed at least partially of an elastic material such as polyurethane.

In some applications, it can also be desirable to employ an irrigationor ablative fluid outside of the instrument (e.g., between the balloonand the target region) to ensure efficient transmission of the radiantenergy when the instrument is deployed. An “ablative fluid” in thiscontext is any fluid that can serve as a transmitter or conductor of theradiant energy. This fluid can be a physiologically compatible fluid,such as saline, or any other non-toxic aqueous fluid that issubstantially transparent to the radiation. In one preferred embodiment,the fluid is released via one or more exit ports at or near the distaltip of the catheter and flows between the balloon and the surroundingtissue, thereby filling any gaps where the balloon does not contact thetissue. The fluid can also serve an irrigation function by displacingany blood within the path of the radiant energy, which could otherwiseinterfere because of the highly absorptive nature of blood with respectto radiant energy at certain wavelengths.

Similarly, if the radiant energy is acoustic, aqueous coupling fluidscan be used to ensure high transmission of the energy to the tissue (andlikewise displace blood that might interfere with the radiant acousticenergy transfer).

The ablative or irrigation fluids of the present invention can alsoinclude various other adjuvants, including, for example,photosensitizing agents and/or pharmacological agents.

In another aspect of the invention, methods are disclosed for selectinga site for cardiac tissue ablation by positioning a guide wire in aportion of the heart; passing a deflectable sheath catheter over theguide wire such that it can be disposed in proximity to a pulmonaryvein; delivering an ablation catheter through the lumen of thedeflectable sheath catheter to the vicinity of the vein; inflating thecompliant balloon at the ostium of the vein and disposing thespot-generating energy emitter at a position suitable to begin theformation of a series of overlapping lesions. The method can furtherinclude continuing formation of overlapping lesions until acircumferential portion of the atrium surrounding the pulmonary vein hasbeen ablated, and then repeating the procedure at one or more additionalpulmonary veins. The method can further include determining whether thecompliant balloon is located in a desired location and/or whetherlesions are properly formed based on images captured by the endoscope.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich like reference numerals designate like parts throughout thefigures, and wherein:

FIG. 1 is a schematic, partially-cutaway view of a cardiac ablationinstrument according to the invention;

FIG. 2A is a schematic view of the cardiac ablation instrument of FIG. 1in a treatment position at the ostium of pulmonary vein;

FIG. 2B is a schematic view of the cardiac ablation instrument of FIG. 1with its compliant balloon inflated and its ablation element deployed atone of a plurality of locations;

FIG. 3 is a schematic illustration of an initial step in performingablative surgery according to the invention, in which a guide wire ispercutaneously inserted into the heart;

FIG. 4 is a schematic illustration of a further step in performingablative surgery in which a deflectable sheath catheter is deployed inthe heart over the guide wire;

FIG. 5 is a schematic illustration of a further step in performingablative surgery in which a deflectable sheath catheter is maneuveredinto a position proximal to a pulmonary vein and the guide wire iswithdrawn and replaced with an ablation catheter according to theinvention;

FIG. 6 is a schematic illustration of a further step in performingablative surgery in which a balloon structure of the present inventionis inflated at the ostium of a pulmonary vein;

FIG. 7 is a schematic view of the cardiac ablation instrument with itscompliant balloon inflated and illustrating how its ablation element canbe deployed at different locations to direct radiant energy throughdifferent regions of the balloon when an asymmetric vein mouth isencountered and further showing how the position of the radiant energyemitter can be adjusted to select a desired location;

FIG. 8 illustrates how a continuous, vein-encircling lesion can beformed by a series of overlapping spot lesions;

FIG. 9 is a schematic block diagram of the components of anendoscope-guided cardiac ablation system according to the invention;

FIG. 10 is a schematic illustration of one embodiment of a radiant lightenergy emitter according to the invention;

FIG. 11 is a schematic exploded view of the optical elements of theemitter of FIG. 10;

FIG. 12 is a schematic illustration of another embodiment of a radiantlight energy emitter according to the invention in which the elementsare configured to project a arc-shaped spot of ablative energy;

FIG. 13 is a schematic illustration of another embodiment of a radiantlight energy emitter according to the invention;

FIG. 14 is a schematic illustration of an alternative embodiment of aradiant energy emitter according to the invention employing ultrasoundenergy;

FIG. 15 is a schematic cross-sectional view of an endoscope useful inthe present invention

FIG. 16 is a schematic illustration of a translation system forindependently positioning the endoscope and ablation components of anendoscope/ablator assembly during a procedure.

DETAILED DESCRIPTION

FIG. 1 provides a schematic, cross-sectional view of an ablationinstrument 10 according to the invention, including an elongate body 14,a central lumen tubing 16 and a compliant balloon 26 inflatable via oneor more ports 22 in the central tubing. The central tubing 16 can alsohouse an energy emitter that is capable of both axial movement androtation within the tubing 12. Within the elongated body (also referredto herein as the catheter body) there can be a plurality of additionallumens, through which certain devices or instruments can been passed.For example, as shown in FIG. 1, the catheter body 14 also provideslumens 18A and 18B for extraction (or circulation) of a inflation fluid,an endoscope 76 and illuminations fibers 28A and 28B. The catheter bodycan carry a marker to assist the clinician in proper placement of thedevice, e.g., a radiopaque marker to aid in fluoroscopic detection.

As shown in FIG. 2A, the instrument is preferably designed such thatupon disposition within the heart (e.g., proximal to a pulmonary vein),the balloon can be inflated such that a shoulder portion 50 of theballoon 26 will be urged into close proximity with a target region 52 ofcardiac tissue (e.g. an region of the atrial heart wall surrounding theostium of a pulmonary vein). As shown in FIG. 2B. the energy emitter (or“lesion generator’) 40 can be positioned to delivery ablative energy 21to the target region 52 to form a lesion.

It should be understood that the embodiments illustrated in the drawingsare only a few of the cardiac ablation instruments that can utilized thepresent invention. Further descriptions of other embodiments can befound, for example, in commonly owned, co-pending U.S. patentapplication Ser. No. 10/357,156, filed Feb. 3, 2003 and U.S. patentapplication Ser. No. 09/924,393, filed Aug. 7, 2001, both of which areexpressly incorporated by reference.

The instrument can optionally include one or more ports for deliveringirrigation fluid to the target region. When the device employs radiantenergy ablation, the fluid is preferably an energy transmissive medium,which helps deliver light, radiation or acoustic energy from a radiantenergy source to a target tissue region. The fluid also serves to clearblood from the vicinity of the instrument and compensate forirregularities in the shape of the heart that might otherwise compromisethe seating of the instrument. The ablative fluid thus provides a cleartransmission pathway external to the balloon.

Returning to FIG. 2B, a radiant energy emitter 40 is shown disposedwithin the projection balloon 26 remotely from the target tissue (e.g.,within a central lumen of the catheter body 14 or otherwise disposedwithin the balloon). In one embodiment, the radiant energy sourceincludes at least one optical fiber coupled to a distal lightprojecting, optical element, which cooperate to project a spot ofablative light energy through the instrument to the target site. Thecatheter body, projection balloon and inflation/ablation fluids are allpreferably substantially transparent to the radiant energy at theselected wavelength to provide a low-loss transmission pathway from theablation element 40 to the target.

Also disposed within the instrument is a reflectance sensor, preferablyan endoscope 76 capable of capturing an image of the target site and/orthe instrument position. The endoscope is typically an optical fiberbundle with a lens or other optical coupler at its distal end to receivelight. The reflectance sensor/endoscope can also include an illuminationsource, such one or more optical fibers coupled to a light source orsources. Endoscopes are available commercially from various sources. Theendoscope can further include an optical head assembly, as detailed inmore detail below, to increase the field of view. In one preferableembodiment, ablation element 40 and endoscope 76 are adapted forindependent axial movement within the catheter body 14.

The term “endoscope” as used herein is intended to encompass opticalimaging devices, generally, including but not limited to endoscopes,fiberscopes, cardioscopes, angioscopes and other optical fiber-basedimaging devices. More generally, “endoscope” encompasses anylight-guiding (or waveguide) structure capable of transmitting an“image” of a object to a location for viewing. The viewing location canbe direct, e.g., an eyepiece, or indirect, e.g., an image capturedevice, such as a CCD camera, which converts image data into a videodisplay.

In certain preferred embodiments, the balloon is a compliant balloon,e.g. an elastic balloon which is expandable to a variable volume toaccommodate pulmonary veins (or other target sites of various sizes,thereby alleviating the need to deploy a balloon catheter instrumentbased on an estimated or assumed vein size and then remove and redeployanother instrument if the cardiac anatomy is different than predicted atthe outset.

FIG. 3 is a schematic illustration of an initial step in performingablative surgery with radiant energy according to the invention, inwhich a guide wire 6 is introduced into a heart 2 and passed into theleft atrium. FIG. 4 is a schematic illustration of a method ofperforming ablative surgery with radiant energy according to theinvention. After guide wire 6 is be introduced into a heart 2 and passedinto the atrium, a deflectable sheath catheter 8 is slid over the guidewire 6. The sheath catheter can be advanced, for example, into the leftatrium of the heart. The guide wire can then be withdrawn and replacedwith a percutaneous ablation instrument 10 according to the invention asshown schematically in FIG. 5. The catheter 10 then be advanced to aposition proximal to the ostium or mouth of a pulmonary vein, as shownin FIG. 6, where its balloon element can be inflated. For this purpose,the catheter 10 can further include at least one internal fluidpassageway (not shown) for inflation of the balloon 26, which is sealedto the body of the catheter 10 by distal seal 21 and proximal seal 22,such that the introduction of an inflation fluid into the balloon 26 caninflate the balloon.

With reference again to FIG. 2B, the balloon 26 is inflated to define aprojection pathway for radiant energy ablation of cardiac tissue. Theexpanded balloon defines a staging through which radiant energy can beprojected in accordance with the invention. In one preferred embodiment,the projection balloon is filled with a radiation-transmissive fluid,such as deuterium oxide (so-called “heavy water”) so that radiant energyfrom an energy emitter can be efficiently passed through the instrumentto a target region 52 of cardiac tissue.

In another aspect of the invention, spot lesions are formed by applyingradiant energy to target tissue in a range from about 50 Joules/cm² toabout 1000 Joules/cm², or preferably from about 75 Joules/cm² to about750 Joules/cm² In certain embodiments, the power levels applied by theenergy emitter can range from about 10 Watts/cm² to about 150 Watts/cm²and the duration of energy delivery can range from about 1 second toabout 1 minute, preferably from about 5 seconds to about 45 seconds, ormore preferably from about 10 to about 30 seconds. For example, forpower levels between 10 and 75 Watts/cm² it can be advantageous to applythe radiant energy for about 30 seconds. Lesser durations, e.g., of 10to 20 seconds, can be used for power levels of 75 to 150 Watts/cm².

The balloons described herein can be preshaped to form parabolic like orvarious other shapes (e.g., to assist in seating the instrument at themouth of a pulmonary vein or otherwise engaging the vein ostium or otheranatomically defined regions of the heart). This can be accomplished,for example, by shaping and melting a polymeric film in a preshaped moldto effect the desired form. Compliant balloons according to the presentinvention can be made, for example, of thin wall polyurethane with amembrane thickness of about 5-50 micrometers, and, in some applications,preferably less than 10 micrometers or less than 5 micrometers inthickness in an inflated state. The balloon is also preferably anelastic or pliable material, e.g., with a durometer ranging from about35A to about 55D, or preferably from about 75A to about 95A, as measuredaccording to the Shore durometer scales.

It should be noted that it is not necessary for the balloon 26 tocontact the target tissue in order to ensure radiant energytransmission. One purpose of the projection balloon is simply to clear avolume of blood away from the path of the energy emitter. With referenceagain to FIG. 2B, an ablative fluid can be employed outside of theinstrument (e.g., between the balloon 26 and the target region 52) viairrigation ports (not shown) to ensure efficient transmission of theradiant energy when the instrument is deployed. The ablative fluid inthis context is any fluid that can serve as a conductor of the radiantenergy. This ablative fluid can be a physiologically compatible fluid,such as saline, or any other non-toxic aqueous fluid that issubstantially transparent to the radiation. The fluid can also serve anirrigation function by displacing any blood within the path of theradiant energy, which could otherwise interfere with the radiant lightenergy transmission to the target region 52.

For alternative designs for delivery of ablative and/or irrigationfluids, see commonly-owned, U.S. patent application Ser. No. 09/660,601,filed Sep. 13, 2000 entitled “Balloon Catheter with Irrigation Sheath,”the disclosures of which are hereby incorporated by reference. Forexample, in one embodiment described in patent application Ser. No.09/660,601, the projection balloon can be partially surrounded by asheath that contains pores for releasing fluid near or at the targetablation site. One of ordinary skill in the art will readily appreciatethat such pores can vary in shape and/or size. A person having ordinaryskill in the art will readily appreciate that the size, quantity, andplacement of the fluid ports of various designs can be varied to providea desired amount of fluid to the treatment site.

In one illustrated embodiment, shown in more detail below, the energyemitter 40 can be a radiant energy emitter and includes at least oneoptical fiber 42 coupled to a distal light projecting, optical element43, which cooperate to project a spot of ablative light energy throughthe instrument to the target site. The optical element can furthercomprise one or more lens elements and/or refractive elements capable ofprojecting a spot or arc-shaped beam of radiation. Alternatively, thelesion generator may generate a annulus or partial ring of ablativeradiation, as described in more detail in commonly owned U.S. Pat. No.6,423,055 issued Jul. 22, 2002, herein incorporated by reference.

In one preferred embodiment, the optical element is adapted to projectan arc-like pattern of radiation and the energy emitter can be rotatedand/or translated to encircle the pulmonary vein. Alternatively, theradiant energy emitter can be an ultrasound or microwave energy source,as described in more detail below that is likewise configured togenerate a series of vein-encircling spot lesions.

FIGS. 7 and 8, taken together, also illustrate an advantageous featureof the present invention, namely, the ability to select the location ofa lesion independent of the instrument design or location. Because theradiant energy emitter does not require contact with a target tissueregion and is, in fact, decoupled from the rest of the instrument, thepresent invention permits the clinician to select a desired targetregion by simply moving the emitter (e.g., within the lumen of thecatheter). As shown in FIG. 7, the radiant energy emitter can bepositioned to form a wide circumferential lesion (when the shape of thepulmonary vein ostium warrants such a lesion) by positioning the radiantenergy emitter at the rear of the projection balloon—at a distance fromthe target tissue denoted as “C”. Alternatively, a smaller diameterlesion can be formed by positioning the radiant energy emitter closer tothe front of the projection balloon, as shown in positions “A” or “B”.Smaller lesions can be preferable when the geometry of the vein ostiumpresents a sharper change in diameter, as shown by schematic wallsegment 4B. It should be appreciated that it may be desirable to changethe intensity of the emitted radiation depending upon the distance itmust be projected; thus a more intense radiant energy beam may bedesirable in the scheme illustrated in position “C” in comparison withposition “A.”.

In addition, the expandable element can include one or more orientationmarkers 57 that can be visualized endoscopically, to aid in determiningthe location of tissue contact or targeted energy delivery relative togeometric features of the expandable element. For example, theorientation marker 57 may take the form of an endoscopically visiblecircumferential line on the portion of the expandable element thatgenerally presents the largest diameter upon inflation. In theendoscopic view this line appears as circle. This circles acts as anaide in determining the optimal amount of energy to deliver to a givenportion of tissue when the tissue is viewed endoscopically. When energyis delivered substantially near the circle as seen in the endoscopicview the operator will select a larger amount energy since energydelivery near the circle is know to be energy delivery substantiallynear the maximum diameter of the expandable element. If energy isdelivered substantially outside of or substantially inside of the circlethe user will know to deliver a lower amount of energy since suchdeliveries are substantially near the smaller diameter proximal anddistal portions of the expandable element respectively. In a similarmanner the expandable element may contain a series of circumferentiallines corresponding to generally differing diameters and appearing asgenerally concentric circles in the endoscopic view each circle beingassociated with an amount of energy generally corresponding to theassociated diameter of the expandable element. These concentric circlesmay also be radiopaque and visible fluoroscopically as a further aid tounderstanding the geometric relationship of the balloon to the complexleft atrial anatomy.

The energy emitter 40 and catheter body 14 can each include one or moremarkers (shown schematically as elements 33 and 35 respectively) to aidin determining the location or tracking movements of the elements.Markers 33 and 35, for example, can be radiopaque lines that canvisualized fluoroscopically.

In addition, the expandable element or the catheter body can include anorientation marker 35 which can be visualized both fluoroscopically andendoscopically or alternatively the catheter body or expandable elementmay include an orientation marker that can be visualizedfluoroscopically and whose location relative to a characteristic featureof the device which can be seen endoscopically is known. These markersare used to visualize the position and/or rotational orientations of thecatheter body relative to the patients anatomy. Each of the markers 35can be suitably shaped to provide rotational information when viewedfluoroscopically. For example, the markers can be shaped in the form ofan “L” to assist in understanding the rotational orientation. Once therotational orientation of the catheter body is know the endoscopic viewmay be rotated either by electronically manipulating the video image orby rotating the endoscope fiber relative to the video camera. The goalof rotating the image is to achieve an orientation such the user mayunderstand where on the endoscopic image the superior, posterior,inferior etc. aspect of the pulmonary vein is located. This informationis important for two reasons. First two anatomical structures to beavoided during pulmonary vein ablation are the phrenic nerve and theesophagus. Both these structures are located near the posterior portionof the left atrium. Generally lower amounts of energy are preferred tobe used when ablating the posterior regions of the veins. Alternativelyscrupulous attention to output temperature probes typically placed inthe lumen of the esophagus is paid when ablating the posterior aspect ofpulmonary veins. Secondly the anterior aspect of some pulmonary veinssuch as the right superior pulmonary vein are know to generally bethicker than other parts of the veins an consequently a higher energydose is desired in these regions. Various other marker mechanisms, suchas magnetic, capacitive or optical markers, can also be used. Thedeflectable sheath used to introduce the catheter can be similarlymarked to assist in fluoroscopic observation.

If the catheter itself is constructed of a low modulus material, it maybe desirable to reinforce it to make more rotationally stable. Forexample, the catheter can be reinforced by one or more longitudinal ribelements or a braid layer so that it can be more easily “torqued” toovercome endoscopic blind spots or other achieve a desired orientation.

Typically with prior art devices, the target site, e.g., the ostium of apulmonary vein, can only be located by fluoroscopic inspection duringinjection of a contrast medium into the vein. Such images are transient.Location of the ablation catheter itself, even with radiopaque markers,is likewise difficult because of the geometry of the heart. Moreover theheart's structure is largely invisible during fluoroscopic inspection.

Endoscopic guidance systems coupled with the use of orientation markerscan help overcome these problems. The use of radiopaque markers on theendoscope and/or the catheter allow the user to orient the ablationinstrument relative to the pulmonary vein and permit anatomical featuresseen via the endoscope to be combined with fluoroscopic information.Orientation markers, such as elements 33 and 35 can be used to determinethe angular position of the instrument relative to structures such theostia and also provide a measure of how far a movable element, such asthe energy emitter 40, has been advanced within the instrument. (Itshould be appreciated that numerous other marker schemes can be employedto achieve these objectives, including ring markers on either the energyemitter and/or the catheter body.)

Similarly, the ring marker shown as element 57 on the projection balloon26 can be replaced by a series of rings. Alternatively, if the endoscopeis maintained in a fixed position relative to the balloon, physicalmarkers can be replaced with virtual markers generated electronically aspart of the display. Such information is particularly useful inselection one or more of alternative sites for ablation. In addition tothe movable energy emitters described herein, the invention can be usedin conjunction with two or more fixed ablation elements (e.g., resistiveheating bands of different circumferences) to select the mostappropriate one (or set) of the ablation elements to be activated forlesion formation.

The endoscopic guidance systems of the present invention can further beused to position any movable point source of ablative energy, e.g., arotating contact or radiant ablation element in lieu of a slidablypositionable source or together therewith, such that the desired pathfor circumferential can be visualized and followed by the ablationelement. Most generally, the endoscopic guidance systems of theinvention can be used together with various fluoroscopic or otherimaging techniques to locate and position any one of the variousinstruments necessary for cardiac ablation.

The ability to position the energy emitter, especially when radiantlight is employed as the ablation modality, also permits endoscopicaiming of the energy. For example, an aiming light beam can betransmitted via the catheter to the target site such that the physiciancan visualize where the energy will be delivered. Thus, endoscopicguidance permits the user to see where energy will be projected atvarious locations of the energy emitter. Thus, if the instrument isdesigned to project light in an annular ring (or arc or spot) around theostium of a pulmonary vein, the aiming beam can be projected down thesame optical delivery path as would the radiant energy. If the “aimingbeam” is projected onto a region of the atrium where a cleartransmission pathway is seen (e.g., there is continuous contact (or thedesired lesion path is otherwise cleared of blood), then the physiciancan begun the procedure. If, on the other hand, a clear transmissionpathway is not seen at a particular location of the ablation element,then the ablation element can be moved until a clear lesion pathway isfound.

Although this “aiming” feature of the invention has been described inconnection with radiant light energy sources, it should be clear that“aiming” can be used advantageously with any radiant energy source and,in fact, it can also assist in the placement of fixed or contact-basedablation elements. Most generally, endoscope-guidance can be combinedwith an aiming beam in any cardiac ablation system to improvepositioning and predetermination of successful lesion formation.

The terms “visual,” “visualize,” “observe” and derivatives thereof areused herein to describe both human and machine uses of reflectance data.Such data can take the form of images visible to a clinician's eye orany machine display of reflected light, e.g., in black & white, color orso-called “false color” or color enhanced views. Detection and displayof reflected energy measurements outside the visible spectrum are alsoencompassed. In automated systems such visual data need not be displayedbut rather can be employed directly by a controller to guide theablation procedure.

FIG. 7-8 further illustrates the unique utility of themulti-positionable, radiant energy ablation devices of the presentinvention in treating the complex cardiac geometries that are oftenencountered. As shown in the figure, the mouths of pulmonary veinstypically do not present simple, funnel-shaped, or regular conicalsurfaces. Instead, one side of the ostium 4B can present a gentlesloping surface, while another side 4A presents a sharper bend. Withprior art, contact-heating, ablation devices, such geometries willresult in incomplete lesions if the heating element (typically aresisting heating band on the surface of an expandable element) can notfully engage the tissue of the vein or ostium. Because the position ofthe heating band of the prior art devices is fixed, when it does notfully contact the target tissue, the result is an incompletely formed,partially circumferential, lesion that typically will be insufficient toblock conduction.

FIG. 7 illustrates how the slidably positionable energy emitters of thepresent invention can be used to avoid this problem. Three potentialpositions of the emitter 40 are shown in the figure (labeled as “A”, “B”and “C”). As shown, positions A and C may not result in optimal lesionsbecause of gaps between the balloon and the target tissue. Position B,on the other hand, is preferable because circumferential contact hasbeen achieved. Thus, the independent positioning of the energy sourcerelative to the balloon allows the clinician to “dial” an appropriatelyring size to meet the encountered geometry. (Although three discretelocations are shown in FIG. 4, it should be clear that emitter can bepositioned in many more positions and that the location can be varied ineither discrete intervals or continuously, if so desired.)

Moreover, the geometries of the pulmonary veins (or the orientation ofthe projection balloon relative to the ostia) may be such that no singleannular lesion can form a continuous conduction block. Again, thepresent invention provides a mechanism for addressing this problem byrotation and adjustment of the location of the energy emitter to form aseries of spot lesions that overlap and create a circumferential block.As shown in FIGS. 14A and 14B, the devices of the present invention canform a first series of lesions 94A, 94B, 94C, etc. by rotation along afirst arc when the energy emitter is in a first location and a secondseries of lesions 96A, 96B, 96C, etc. by rotation along a second arcwhen the energy emitter is in a second location. Because each spotlesion has an area (dependent largely by the amount of energy depositedinto the tissue) the spot lesions can combine, as shown, to form acontinuous encircling or circumscribing lesion that blocksfibrillation-inducing electric conduction. Although illustrated as twoseries of spot lesions along two curved paths, it should be clear thatany number of paths (emitter locations) can be chosen in order tocomplete vein isolation. Moreover, the size of the spots can be varied,e.g., by depositing more energy in a particular location, in the courseof a procedure.

FIG. 9 is a schematic block diagram shown the endoscope/ablator assembly32 comprising endoscope 76 and ablation element 40 connected to ananalyzer system. The analyzer system further includes a detector 34 fordetecting reflected light (and preferable for generating a image). Theoutput of the detector 34 can be transmitted to a display 36 forclinician viewing. The display 36 can be a simple eyepiece, a monitor ora heads-up projection onto glasses worn by members of the surgical team.The system can further include an energy source 39, a controller 37 anda user interface 38. In use, the endoscope 76 captures images which canbe processed by the detector 34 and/or controller 37 to determinewhether a suitable ablation path can be created. An aiming light source31 can also be used visualize the location where energy will be deliveryto the tissue. If a suitable ablation path is seen by the surgeon, thecontroller 37 can transmit radiant energy from the ablation element 39to a target tissue site to effect ablation. The controller can furtherprovide simulated displays to the user, superimposing, for example, apredicted lesion pattern on the image acquired by the detector orsuperimposing dosimetry information based on the lesion location. Thecontroller can further include a memory for storing and displaying data,such as pre-procedure images, lesion predictions and/or actual outcomes.The controller can further provide a safety shutoff to the system in theevent that a clear transmission pathway between the radiant energysource and the target tissue is lost during energy delivery.

FIG. 10 is a schematic cross-sectional illustration of one embodiment ofa radiant energy emitter 40A according to the invention. FIG. 11 is aschematic perspective view of the principal optical components of theemitter. In one preferred embodiment, the radiant energy iselectromagnetic radiation, e.g., coherent or laser light, and the energyemitter 40A projects an beam of radiation that forms a spot orarc-shaped exposure pattern upon impingement with a target surface. Forexample, radiant energy emitter 40A can include an optical fiber 42, thedistal end of which is beveled into an energy-emitting face 44 ofreduced cross-section. the fiber 42 passes an beam of light to agradient index (GRIN) lens 46, which serves to collimate the beam,keeping the beam width the substantially the same, over the projecteddistance. The beam that exits the GRIN lens is reflected by reflector 48in an angular direction from about 5 degrees to about 110 degreesrelative to from the light's path along the longitudinal axis of thecatheter. Generally, the angle of reflection from the central axis ofthe optical fiber 42 can range from about 30 to nearly 90 degrees. Inother words, the angle of projection, from the optical axis of the fiber42 (or lens 46) will be between about 5 to 60 degrees forward ofperpendicular.

FIG. 12 is a schematic illustration of a variant on the optical assemblyof FIGS. 10 and 11, in which the beveled distal end 44 of the fiber 42is offset from the centerline 111 of the longitudinal axis, causinglight propagating through the GRIN lens 46 to be bent into an arc-shapedexposure pattern. Overlapping patterns of such arc-shaped spots can beused advantageously to form an encircling lesion. The subtended angle ofprojected annular light, a, can be between about 20 and about 60degrees, preferably between about 25 and about 35 degrees, mostpreferably in some applications about 30 degrees.

FIG. 13 is a schematic illustration of another embodiment of a radiantenergy emitter 40A according to the invention. Again, in thisembodiment, the radiant energy is electromagnetic radiation, e.g.,coherent or laser light, and the energy emitter 40A projects a beam ofradiation that forms a spot or arc-shaped exposure pattern uponimpingement with a target surface. For example, radiant energy emitter40A can include an optical fiber 42 again having a beveled distal tipoffset from the central axis. Ablative energy entering the gradientindex (GRIN) lens 46 will be formed into an arc-shaped beam of light.The GRIN lens 46 also serves to collimate the beam, keeping the beamwidth the same, over the projected distance. The beam that exits fromthe GRIN lens 46 will be refracted first in the air gap 45 of the distalend cap and again as it passed through the wall of the end cap. Theprojected light beam will expand (in diameter) over distance, but theenergy will remain largely confined to a narrow annular band. Generally,the angle of projection, β, from the optical axis of the fiber 42 (orlens 46) will be between about 5 to 60 degrees forward of perpendicular.Again, the subtended angle of the arc-shaped spots can be between about20 to about 60 degrees, preferably between about 25 and about 35degrees, most preferably in some applications about 30 degrees.

The diameter of the beam of light will be dependent upon the distancefrom the point of projection to point of capture by a surface, e.g., atissue site, e.g., an interstitial cavity or lumen. Typically, when thepurpose of the radiant energy projection is to form a transmural cardiaclesion, e.g., around a pulmonary vein, the diameter (or minimum width)of the beam will be between about 6 mm and about 20 mm, preferablygreater than 10 mm or greater than 15 mm. In some instances a beam widthgreater than 20 mm can also be useful. The cross-sectional area of thebeam at tissue impingement can range from about 5 mm² to about 500 mm²to form lesions having average surface areas of the same or similarsizes. In some applications is preferable to control the spot size tocreate lesions having surface areas of less than about 100 mm². When thespot is arc-shaped as shown in FIGS. 14A and 14B, the subtended angle ofprojected annular light is between about 20 and about 60 degrees,preferably between about 25 and about 35 degrees, most preferably insome applications about 30 degrees.

Preferred energy sources for use with the percutaneous ablationinstruments of the present invention include laser light in the rangebetween about 200 nanometers and 2.5 micrometers. In particular,wavelengths that correspond to, or are near, water absorption peaks areoften preferred. Such wavelengths include those between about 805 nm andabout 1070 nm, preferably between about 900 nm and 1100 nm, mostpreferably, between about 960 nm and 1000 nm. In certain embodiments,wavelengths around 915 nm or around 960 nm around 980 nm can bepreferred during endocardial procedures. Suitable lasers include excimerlasers, gas lasers, solid state lasers and laser diodes. One preferredAlGaAs diode array, manufactured by Spectra Physics, Tucson, Ariz.,produces a wavelength of 980 nm.

The optical waveguides, as described in above, can be made frommaterials known in the art such as quartz, fused silica or polymers suchas acrylics. Suitable examples of acrylics include acrylates,polyacrylic acid (PAA) and methacrylates, polymethacrylic acid (PMA).Representative examples of polyacrylic esters include polymethylacrylate(PMA), polyethylacrylate and polypropylacrylate. Representative examplesof polymethacrylic esters include polymethylmethacrylate (PMMA),polyethylmethacrylate and polypropylmethacrylate.

Internal shaping of the waveguide can be accomplished by removing aportion of material from a unitary body, e.g., a cylinder or rod.Methods known in the art can be utilized to modify waveguide to havetapered inner walls, e.g., by grinding, milling, ablating, etc. In oneapproach, a hollow polymeric or glass cylinder, e.g., a tube, is heatedso that the proximal end collapses and fuses together, forming anintegral proximal portion which tapers to the distal end of thewaveguide. In another approach, the conical surface 45 can be formed ina solid quartz cylinder or rod by drilling with a tapered bore.

Waveguide 44 can be optical coupled to optical fiber 42 by variousmethods known in the art. These methods include for example, gluing, orfusing with a torch or carbon dioxide laser. In one embodiment,waveguide 44, optical fiber 42 and, optionally, a gradient index lens(GRIN) 46 are in communication and are held in position by heatshrinking a polymeric jacket material 49, such as polyethyleneterephthalate (PET) about the optical apparatus 40.

FIG. 15 illustrates an alternative embodiment of a radiant energyemitter 40C in which an ultrasound transducer 60, comprising individualshaped transducer elements (and/or lenses or reflectors) 62 which direct(project) the ultrasound energy into a spot of energy that can likewiseform an annular exposure pattern upon impingement with a target surface.The emitter 40C is supported by a sheath 66 or similar elongate body,enclosing electrical leads, and thereby permitting the clinician toadvance the emitter through an inner lumen of the instrument to adesired position for ultrasound emission.

Yet another embodiment of a radiant energy emitter can employ microwaveenergy similarly focused into a spot or arc-shaped exposure beam. Themicrowave energy emitter can include a coaxial transmission line (orsimilar electrical signal leads) and a helical coil antenna. Radiationreflectors can cooperate to shield and direct the radiation into a spot.In other embodiments, a radioisotope or other source of ionizingradiation can be used in lieu of the microwave antenna, again withappropriate radiation shielding elements to project a beam of ionizingradiation.

It should be clear that the invention can be practiced with variousnumbers of illuminating and/or sensing elements, and with or without useof the energy emitter as an element in the contact sensing module. Theemitter and the endoscope can each move independently, if desired.Moreover, ultrasound emitters and detectors can also be used in the samemanner in lieu of the light reflecting mechanisms to determine contact.In any event, the output signals of the sensors can be electronicallyprocessed and incorporated into a display.

The devices of the present invention can further include illuminationelements that are capable of diffusing light to a large contact area oftissue by employing a scattering medium at the distal end of theillumination fiber. Examples of this diffusing material can be a matrixof titanium dioxide particles suspended in cured silicone. Thisdiffusing medium allows high intensity light to be uniformly diffusedover a large area preferably over an area greater than 40 mm indiameter.

Endoscopes useful in the present invention can include a coherentoptical fiber bundle for transmitting the captured image back to adetector and display. The distal end of the endoscope can be coupled toa set of lenses which create an image at the distal end of the fiberbundle and provide an enhanced field of view. Such field enhancingelements preferably increase the field of view to greater than 50degrees, more preferably to about 70 degrees or higher. Typically,commercially available endoscopes have a field of view of about 50degrees or less in air. However, when immersed in water or similarfluids, the field of view of the endoscope is further reduced due to therefractive index difference between water and air. As explained in moredetail below, a greater field of view can be very important toendoscopic guidance.

The endoscopes of the present invention provide the ability to positionthe percutaneous ablation instruments of the present invention at atreatment site such that proper location of the energy emitter vis-à-visthe target tissue (as well a satisfactory degree of contact between theprojection balloon and the tissue) is achieved.

FIG. 15 provides a detailed schematic illustration of an endoscope 76Awith enhanced field of view. The endoscope can include a fiber bundle130 within a protective polyimide tube 132 coupled to distal stainlesssteel tube 134 in which the field-enhancing optics are disposed. Withindistal tube 134, an imaging lens 136 and an objective lens 140 aresituated, together with a centering and connecting tubes (e.g., tube 135and 142) as may be needed to secure the lenses in place. (It should beappreciated that various lens combination or compound lens structurescan be substituted for the elements shown in FIG. 15.)

The endoscope 76A is designed to have a wide field of view even while itis immersed in liquid. The liquid in which it is immersed typically canbe either physiological saline in the inner lumen of the catheter ordeuterium oxide which is one preferred medium for filling applicants'projection balloon. Both of these liquids have essentially the sameindex of refraction. To achieve the wide field of view a lens systemsuch as shown in FIG. A can be used. The lens system consists of twoplano-convex lenses 136 and 140 arranged as shown along with anapertured window 144. High index of refraction materials are preferablyused for the lenses. Suitable materials include sapphire, cubic zirconiaor high index glass materials. Alternatively, air-filled opticalstructures can be substituted for the solid lenses shown in the figure.All these materials are readily available as small diameter spheres withoptical quality surfaces. The spheres can be made into hemispheres andthe diameter of the hemispheres are reduced using common lens grindingtechnology. The aperture can be constructed by metallizing one surfaceof flat glass plate. The central aperture hole is created by masking theflat glass before the metallization or removing the metallization with alaser.

The ability have a field of view greater that 50 degrees (and,preferably, in some applications, greater than 70 degrees, or 90degrees) can be important because of the geometry of the heart and theablation elements. Visualization of the ostium of a pulmonary veininherently requires a wide field of view. Moreover, the ablation element(including any expandable element) must be short because of the limitedspace available within the atrial chamber. These two factors combine torequire the placement of the endoscope close to the vein and an evenwider field of view is desirable, typically greater than 70 degrees, inorder to visualize the target region and the instrument's positionrelative to the target region. Moreover, the wide field of view allowsthe clinician to see well proximal to the apex of the balloon; thusproviding the ability to determine if the instrument is placed too deepin the pulmonary vein.

Thus, formation of ablative lesions for treatment of atrialfibrillations and the like can be accomplished with the instruments andsystems described herein by observing balloon location via an endoscopedeployed within applicants' catheter devices. For example, the methodcan include observation of a marker on the balloon to determineorientation of a balloon (or other expandable element) within the heart.The method can further include projecting an aiming beam during (e.g.,while or following) positioning of the energy emitter to identify acandidate site for treatment. Preferably, the aiming beam issubstantially coaxial with the treatment energy beam and the spot formedby the aiming beam is coincident (e.g., substantially overlaps) with thesite to be ablated. In a preferred embodiment, the aiming beam isintroduced via a beam combining mirror arrangement (as shown in FIG. 9)such that the aiming beam is projected via the same optical fiber, lensand reflector elements as the treatment beam. The aiming beam can verifythat a candidate site is acceptable for ablation by endoscopicobservation of where the aiming beam impinges. Any visible wavelengthincluding white light can be used as the aiming beam, however, incertain applications it can be advantageous to employ two or morediscrete wavelengths, e.g. red and green light, to visualizing bothtissue contact and blood.

Verification can be based on endoscopic observation of balloon contactwith tissue in the vicinity of the aiming beam impingement—or on similarobservations of a lack of balloon contact with blood in the vicinity ofthe aiming beam impingement. The aiming beam can, thereby, be used todetermine the topography of the cardiac tissue at a candidate site,assess the quality of contact and/or lack of blood occlusion. Coupledwith endoscopic observation of lesions as they are formed, the aimingbeam can further be used to predict the path of future therapy and“line-up” the next candidate site to ensure the formation of contiguous(overlapping) spot ablations and, ultimately, a continuousvein-encircling lesion.

Endoscopic observation can also be used to select a dose for forming aspot lesion based on endoscopic observation following expansion of theexpandable member and positioning of the energy emitter. For example, adose can be selected based on an observed size of an impingement spot ofan aiming beam or based on an observed balloon location.

The methods of the present invention can further include forming a firstspot lesion and then repositioning the energy emitter to a secondlocation. Next, visualization can be used to verify a second candidatesite is acceptable for ablation by endoscopic observation of a aimingbeam during repositioning of the energy emitter. Such visualization ofobservation can further be used to determine that a second (orsubsequent candidate site) is suitable to forming a subsequent lesionthat will be contiguous with the first lesion.

The endoscopes of the present invention can also be used in conjunctionwith other optical reflectance measurements of light scattered orabsorbed by blood, body fluids and tissue. For example, white lightprojected by an illumination source toward tissue has several componentsincluding red and green light. Red light has a wavelength range of about600 to about 700 nanometers (nm) and green light has a wavelength rangeof about 500 to about 600 nm. When the projected light encounters bloodor body fluids, most if not all green light is absorbed and hence verylittle green or blue light will be reflected back toward the opticalassembly which includes a reflected light collector. As the apparatus ispositioned such that blood and body fluids are removed from thetreatment field cleared by an inflated balloon member, the reflectanceof green and blue light increases as biological tissue tends to reflectmore green light. As a consequence, the amount of reflected green orblue light determines whether there is blood between the apparatus andthe tissue or not.

Thus, the endoscopic displays of the present invention can incorporatefilters (or generate “false-color” images) that emphasize the presenceor absence of blood in the field. For example, when the inflated balloonmember contacts the heart tissue (or is close enough that the balloonand ablative fluid released by the instrument form a clear transmissionpathway), more green light will be reflected back into the opticalassembly and the collector. The ratio of two or more differentwavelengths can be used to enhance the image. Accordingly, acolor-enhanced endoscope can permit visualization of the instrumentand/or the target site, as well as a determination of whether bloodprecludes the formation of a continuous lesion, e.g., circumferentiallesion around the ostium of a pulmonary vein.

Alternatively, spectrographic measurements can be taken in tandem withendoscopic imaging, Thus, reflected light can be transmitted backthrough a collector, such as an optical fiber to a spectrophotometer.The spectrophotometer (Ocean Optics Spectrometer, Dunedin, Fla., modelS-2000) produces a spectrum for each reflected pulse of reflected light.Commercially available software (LabView Software, Austin, Tex.) canisolate values for specific colors and perform ratio analyses.

Once the operator is satisfied with the positioning of the instrument,radiant energy can then be projected to the target tissue region. If theradiant energy is electromagnetic radiation, e.g., laser radiation, itcan be emitted onto the tissue site via a separate optical fiber or,alternatively, through the same optical fiber used for transmitting thewhite, green or red light. The laser light can be pulsed intermittentlyin synchronous fashion with the positioning/reflecting light to ensurethat the pathway remains clear throughout the procedure.

In FIG. 16, a translatory mechanism 80 is shown for controlled movementof a radiant energy emitter within the instruments of the presentinvention. The exemplary positioner 80 is incorporated into a handle 84in the proximal region of the instrument, where the elongate body 82 ofthe radiant energy emitter 40 engages a thumb wheel 86 to controladvancement and retraction of the emitter. It should be clear thatvarious alternative mechanisms of manual or automated nature can besubstituted for the illustrated thumb wheel 86 to position the emitterat a desired location relative to the target tissue region.

In addition, as shown in FIG. 16, the elongate body 82 that supports theradiant energy emitter 40 can further include position indicia 92 on itssurface to assist the clinician in placement of the ablation elementwithin the instrument. The handle can further include a window 90whereby the user can read the indicia (e.g., gradation markers) to gaugehow far the emitter has been advanced into the instrument.

The assembly 32 can further include an endoscope translatory mechanism98 as shown in FIG. 16 for controlled movement of the reflectance sensoror endoscope 76 within the instruments of the present invention. Theexemplary positioner 98 can be incorporated into a handle 99 in theproximal region of the instrument, where the elongate body of the sensor76 engages a thumb wheel 97 to control advancement and retraction of theemitter.

The apparatus of the present invention thus permits the selection of anablative lesion, e.g., a circumferential lesion, of desired shape andsize. This adjustability can be used advantageously to form a lesion ata desired location, or along a desired path, to effectively blockconduction and thereby treat atrial fibrillation.

Although described in connection with cardiac ablation procedures, itshould be clear that the instruments of the present invention can beused for a variety of other procedures where treatment with radiantenergy is desirable, including laparoscopic, endoluminal, perivisceral,endoscopic, thoracoscopic, intra-articular and hybrid approaches.

The term “radiant energy” as used herein is intended to encompass energysources that do not rely primarily on conductive or convective heattransfer. Such sources include, but are not limited to, acoustic andelectromagnetic radiation sources and, more specifically, includemicrowave, x-ray, gamma-ray, ultrasonic and radiant light sources. Theterm “light” as used herein is intended to encompass electromagneticradiation including, but not limited to, visible light, infrared andultraviolet radiation.

The term “continuous” in the context of a lesion is intended to mean alesion that substantially blocks electrical conduction between tissuesegments on opposite sides of the lesion. The terms “circumferential”and/or “curvilinear,” including derivatives thereof, are herein intendedto mean a path or line which forms an outer border or perimeter thateither partially or completely surrounds a region of tissue, or separateone region of tissue from another. Further, a “circumferential” path orelement may include one or more of several shapes, and may be forexample, circular, annular, oblong, ovular, elliptical, semi annular, ortoroidal.

The term “lumen,” including derivatives thereof, in the context ofbiological structures, is herein intended to mean any cavity or lumenwithin the body which is defined at least in part by a tissue wall. Forexample, cardiac chambers, the uterus, the regions of thegastrointestinal tract, the urinary tract, and the arterial or venousvessels are all considered illustrative examples of body spaces withinthe intended meaning.

The term “catheter” as used herein is intended to encompass any hollowinstrument capable of penetrating body tissue or interstitial cavitiesand providing a conduit for selectively injecting a solution or gas,including without limitation, venous and arterial conduits of varioussizes and shapes, bronchoscopes, endoscopes, cystoscopes, culpascopes,colonscopes, trocars, laparoscopes and the like. Catheters of thepresent invention can be constructed with biocompatible materials knownto those skilled in the art such as silicone rubber, polyethylene,Teflon, polyurethanes, nylon, polycarbonate, including blends andcopolymers such PEBAX, etc. The term “lumen” including derivativesthereof, in the context of catheters is intended to encompass anypassageway within a catheter instrument (and/or track otherwise joinedto such instrument that can serve as a passageway) for the passage ofother component instruments or fluids or for delivery of therapeuticagents or for sampling or otherwise detecting a condition at a remoteregion of the instrument. The term “catheter” is also intended toencompass any elongate body capable of serving as a conduit for one ormore of the ablation, expandable or sensing elements described herein,e.g., energy emitters, balloons and/or endoscopes. Specifically in thecontext of coaxial instruments, the term “catheter” can encompass eitherthe outer catheter body or sheath or other instruments that can beintroduced through such a sheath. The use of the term “catheter” shouldnot be construed as meaning only a single instrument but rather is usedto encompass both singular and plural instruments, including coaxial,nested and other tandem arrangements.

The term “vessel” or “blood vessel” includes, without limitation, veins,arteries, and various chambers or regions of the heart, such as theatria, ventricles, coronary sinus, vena cava and, in particular, theostia or antrum of the pulmonary veins.

It should be understood that the term “balloon” encompasses deformablehollow shapes which can be inflated into various configurationsincluding spherical, obloid, tear drop, etc., shapes dependent upon therequirements of the body cavity. Such balloon elements can be elastic orsimply capable of unfolding or unwrapping into an expanded state. Theballoon can further encompass multiple chamber configurations.

The term “transparent” is well recognized in the art and is intended toinclude those materials which allow transmission of energy through, forexample, the primary balloon member. Preferred transparent materials donot significantly impede (e.g., result in losses of over 20 percent ofenergy transmitted) the energy being transferred from an energy emitterto the tissue or cell site. Suitable transparent materials includefluoropolymers, for example, fluorinated ethylene propylene (FEP),perfluoroalkoxy resin (PFA), polytetrafluoroethylene (PTFE), andethylene-tetrafluoroethylene (ETFE) or polyester resins includingpolyethylene teraphathalate (PET).

One skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims. Allpublications and references cited herein are expressly incorporatedherein by reference in their entirety.

1. A cardiac tissue ablation system, comprising: an elongate catheterconfigured to deliver a distal end thereof to a patient's heart; anexpandable member formed at the distal portion of the catheter, theexpandable member having an elastic portion configured to conform to theshape of a target tissue region upon expansion; and an energy emittermovably disposed within a lumen of the catheter, the energy emitterconfigured to deliver a series of spots of radiant ablative energy tothe target tissue region.
 2. The system of claim 1, wherein the energyemitter is configured such that the spots of energy result in a seriesof lesions formed in the target tissue region when the emitter isactivated, the lesions having an average area ranging from about 5 mm²to about 100 mm².
 3. The system of claim 2, wherein the energy emitteris configured to form arc shaped lesions in the target tissue regionsubtending an angle ranging from about 5 degrees to about 45 degreesrelative to the emitter.
 4. The system of claim 2, wherein the energyemitter is configured to form arc shaped lesions in the target tissueregion subtending an angle of less than about 30 degrees relative to theemitter.
 5. The system of claim 1, wherein the energy emitter isslidably and rotatably disposed within an inner lumen of the catheterthereby allowing the energy emitter to effectively ablate any of aplurality of regions within the target tissue area.
 6. The system ofclaim 1, wherein the energy emitter is configured to project energytoward the target tissue area at an angle ranging from about 5 degreesto about 110 degrees relative to a longitudinal axis of the catheter. 7.The system of claim 1, wherein the energy emitter is configured toproject energy toward the target tissue area at an angle ranging fromabout 60 to about 90 degrees relative to a longitudinal axis of thecatheter.
 8. The system of claim 6, wherein the energy emitter includesa reflector element coupled to a distal end of the energy emitter. 9.The system of claim 8, wherein the reflector element is a quartzreflector.
 10. The system of claim 1, wherein the energy emitterincludes an optic fiber with a grin lens coupled to a distal end of thefiber, the energy emitter further having a reflector element positioneddistal of the grins lens, the reflector element configured to deliverablative energy to the cardiac tissue at an angle of about 900 relativeto a longitudinal axis of the catheter.
 11. The system of claim 1,further including an endoscope configured to allow direct visualizationof the tissue treatment area.
 12. The system of claim 1, wherein theexpandable member includes a plurality of markers defining a number ofpower-level segments, each power-level segment corresponding to anamount of ablation energy to be delivered to the segment by the energyemitter.
 13. The system of claim 10 that further includes at least oneradiopaque marker visible via x-ray imaging shaped in such a manner asto allow the determination of the rotational orientation of theexpandable member relative to the patients anatomy.
 14. The system ofclaim 14 wherein the radiopaque marker resides at a know locationrelative to the view seen in the endoscope such that the orientation ofthe patients anatomy relative to the endoscopic view may be determined.15. The system of claim 1, wherein the expandable member is ablunt-nosed balloon configured to impede passage of the balloon into apulmonary vein when the balloon is deployed in proximity to the vein.16. The system of claim 1, wherein the expandable member is a balloonwith a tapered distal end that impedes passage of the balloon into apulmonary vein when the balloon is deployed in proximity to the vein.17. The system of claim 1 wherein the expandable member is a balloonwhose distal portion gradually decreases in diameter.
 18. A cardiacablation system, comprising: a cardiac ablation catheter having anexpandable member formed on a distal end thereof, the expandable memberformed of an elastic material such that the expandable member conformsto a shape and contour of a target tissue area during expansion of theexpandable member; and a spot energy emitter movably disposed within aninner lumen of the catheter, the spot energy emitter configured todeliver ablative energy to the target tissue area thereby forming a spotlesion in the target tissue area.
 19. The system of claim 13, whereinthe spot energy emitter is configured to project radiant energy to thetarget tissue area at an angle of about 90° or less relative to alongitudinal axis of the catheter.
 20. The system if claim 13, whereinthe spot lesion is an arc shaped lesion subtending an angle of less thanabout 30° relative to the emitter.
 21. A method for treating a cardiaccondition, comprising: delivering an expanding member formed on a distalend of a catheter to a position adjacent a tissue treatment area withina patient's heart, the expandable member having an elastic portionconfigured to conform to the tissue treatment area; expanding theexpandable member thereby allowing the elastic portion of the expandablemember to conform to the tissue treatment area; positioning an energyemitter at a first location within an inner lumen of the catheter; anddelivering a first spot of energy from the energy emitter to the tissuetreatment area thereby resulting in a first spot lesion.
 22. The methodof claim 21, further comprising positioning the energy emitter at asecond location within the inner lumen of the catheter, and delivering asecond spot of energy from the energy emitter to the tissue treatmentarea thereby resulting in a second spot lesion, wherein the second spotlesion intersects the first spot lesion.
 23. The method of claim 22,further comprising repeating the positioning step and the deliveringstep until a plurality of spot lesions are provided which form asubstantially circumferential lesion.
 24. The method of claim 23,wherein the circumferential lesion encircles an ostium of a pulmonaryvein.
 25. The method of claim 24, wherein the cardiac condition isatrial fibrillation
 26. The method of claim 21, wherein each spot lesionis formed in the shape of an arc that subtends an angle ranging fromabout 5 degrees to about 45 degrees relative to the emitter.
 27. Themethod of claim 21, wherein each spot lesion is formed in the shape ofan arc that subtends an angle less than about 30 degrees relative to theemitter.
 28. The method of claim of claim 21 wherein the method furthercomprises observing balloon location via an endoscope deployed withinthe catheter.
 29. The method of claim of claim 28 wherein the methodfurther comprises observing a marker on the balloon to determine balloonorientation within the heart.
 30. The method of claim of claim 21wherein the method further comprises projecting an aiming beam duringpositioning of the energy emitter to identify a candidate site fortreatment.
 31. The method of claim 30 wherein the method furthercomprises verifying that a candidate site is acceptable for ablation byendoscopic observation of the aiming beam.
 32. The method of claim 31wherein the verification is based on endoscopic observation of ballooncontact with tissue in the vicinity of the aiming beam impingement. 33.The method of claim 30 wherein the verification is based on endoscopicobservation of a lack of balloon contact with blood in the vicinity ofthe aiming beam impingement.
 34. The method of claim of claim 21 whereinthe method further comprises selecting a dose for forming a spot lesionbased on endoscopic observation following expansion of the expandablemember and positioning of the energy emitter.
 35. The method of claim ofclaim 34 wherein the method further comprises selecting a dose based onan observed size of an impingement spot of an aiming beam.
 36. Themethod of claim of claim 34 wherein the method further comprisesselecting a dose based on an observed balloon location.
 37. The methodof claim of claim 21 wherein the method further comprises forming afirst spot lesion and then repositioning the energy emitter to a secondlocation.
 38. The method of claim 37 wherein the method furthercomprises verifying a second candidate site is acceptable for ablationby endoscopic observation of a aiming beam during repositioning of theenergy emitter.
 39. The method of claim 38 wherein the method furthercomprises verifying that a second or subsequent candidate site issuitable to forming a subsequent lesion that will be contiguous with thefirst lesion.
 40. An instrument for cardiac ablation comprising anelongated optical fiber capable of transmitting ablative radiation and adistal light projection assembly, the assembly further comprising a bodyfor encasing a distal end portion of the fiber and a reflector forredirecting radiant energy travelling through the fiber at anglerelative to the longitudinal axis of the fiber.
 41. The instrument ofclaim 40 wherein a distal end face of the optical fiber is beveled to adistal output face of reduced cross-sectional area.
 42. The instrumentof claim 41 wherein the output face is generally rectangular.
 43. Theinstrument of claim 40 wherein the distal light projecting assemblyfurther comprises a lens configured to receive radiant energy from adistal output face of the optical fiber and focus the energy prior toredirection by the reflector.
 44. The instrument of claim 43 wherein thelens further comprises at least one graded refractive index lens. 45.The instrument of claim 40 wherein the distal end portion of the opticalfiber is beveled to a distal output face of reduced cross-sectional areaand the distal light projecting assembly further comprises a lensconfigured to receive radiant energy from the distal output face of theoptical fiber and focus the energy prior to redirection by thereflector.
 46. The instrument of claim 45 wherein the beveled outputface of the optical fiber is rectangular and is offset from an opticalaxis of the lens such that the radiant energy is projected as an arcshaped beam.
 47. The instrument of claim 46 wherein the instrument isfurther configured to project a beam of radiant energy in the shape ofan arc that subtends an angle less than about 30 degrees.